TRANSIENT OSCILLATION OF CAVITATION BUBBLES NEAR STONE SURFACE DURINGELECTROHYDRAULIC LITHOTRIPSY

Using high-speed photography and acoustic emission measurements, we st udied the dynamics of a transient cavitation bubble near a stone surfa ce and the concomitant shockwaves generated during electrohydraulic li thotripsy (EHL), At each spark discharge, a vapor plasma and subsequen tly a cavitation bubble oscillating around the tip of an EHL probe are produced, Simultaneously, three distinctive shockwave pulses are gene rated, The first shockwave is produced by the rapid expansion of the v apor plasma, while the second and third waves are produced by rebounds of the cavitation bubble, Depending on the proximity of the probe to the stone surface, the collapse of the cavitation bubble may be symmet ric, resulting in a strong shockwave emission; or asymmetric, leading to the formation of a liquid jet, For the Nortech AUTOLITHTM lithotrip ter with a 1.9F probe that was used in this study, maximum shockwave e mission is produced when the probe is about 1 mm from the stone surfac e, whereas the maximum jet velocity is produced when the probe tip is at distance equivalent to the maximum bubble radius of about 3 mm, The se findings are consistent with clinical experience, which suggests th at for optimal treatment results, the EHL probe should be placed close to the stone surface.